UUID v4 Generator

What a version 4 UUID is

A UUID, universally unique identifier, is a 128-bit value formatted as 32 hexadecimal characters split into five groups. Version 4 UUIDs are the most common type, generated almost entirely from random bits rather than a timestamp or hardware address, with two fixed bit patterns reserved to mark the version and variant, which is what the fixed 4 and the 8, 9, a or b you see in every version 4 UUID actually represent.

Why collisions are not a practical concern

A version 4 UUID has 122 random bits, giving roughly 5.3 times 10 to the 36th possible values. Even generating a billion UUIDs per second, you would need to run for far longer than the age of the universe before the odds of an accidental duplicate became meaningfully non-zero, which is why UUIDs are trusted as unique identifiers across distributed systems without any central coordination.

How this generator produces randomness

Each UUID is built using your browser's crypto.getRandomValues, the same cryptographically secure random number source used for security-sensitive operations like generating encryption keys, rather than Math.random, which is not designed to be unpredictable. The version and variant bits are then set per RFC 4122 before the bytes are formatted into the standard dashed hex string.